1. Field
The following description relates to a repeating technology for providing long-distance transmission and increasing in link capacity in an Ethernet passive optical network (EPON) that supports a service at multiple rates.
2. Description of the Related Art
Currently, a time division multiplexing-passive optical network (TDM-PON) uses 1 Gbps Ethernet PON (EPON) and 2.5 Gbps gigabit capable PON (GPON). Standardization of 1 Gbps Ethernet passive optical network (EPON) technology has been completed in IEEE802.3ah, and 1 Gbps EPON provides uplink/downlink transmission rate of maximum 1 Gbps. In contrast, standardization of 2.5 Gbps GPON technology has been completed in ITU-T G.984.x, and the 2.5 Gbps GPON technology provides a downlink transmission rate of maximum 2.5 Gbps and an uplink transmission rate of maximum 1 Gbps.
With the introduction of various multimedia services of high quality, a need for a transmission rate in an access network has been increasing. Accordingly, in IEEE802.3av standards, 10 Gbps EPON technology has been standardized, and in ITU-T G.987.x, GPON with 10 Gbps/2.5 Gbps has been standardized.
10 Gbps EPON that is standardized in IEEE802.3av has been standardized with architecture and a system that can accommodate all the existing 1 Gbps EPON subscriber, new asymmetric 10 Gbps/1 Gbps EPON subscribers and symmetric 10 Gbps EPON subscribers while using a previously established optical distribution network intact. Thus, 10 Gbps EPON allocates a 1577 nm waveband and a 1490 nm waveband for downstream transmission of 10 Gbps signals and 1 Gbps signals, respectively. Due to the difference in waveband, wavelength division multiplexing overlay (WDM) technique is used for multiplexing and transmitting such signals. In addition, 10 Gbps EPON allocates a 1270 nm waveband and a 1310 nm waveband for upstream transmission of 10 Gbps signals and 1 Gbps signals, respectively.
However, a waveband of about 1260 nm to 1360 nm is used for transmission of 1 Gbps signals, and it overlaps a waveband for transmission of 10 Gbps signals. To solve this problem, an EPON optical line terminal (OLT) divides the upstream transmission time band into a plurality of time slots, and overlapping wavelengths for both 10 Gbps and 1 Gbps signals are present in common in a single optical fiber. The wavelengths division is performed using dual rate physical media dependent (PMD) technique in the EPON OLT. For example, the dual rate PMD may transmit or receive an optical signal transmitted at transmission rates of 1G and 10G.
Researches on a technique for long-distance transmission of an optical signal and an increase in link capacity in an EPON have been actively carried out.